Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$42.41	11.628%	$47.3414	$47.34	$47.35	$47.30
Purchase #2	$126.82	5.263%	$133.4945	$133.49	$133.50	$133.50
Purchase #3	$117.82	11.381%	$131.2291	$131.23	$131.25	$131.20
Purchase #4	$9.89	10.159%	$10.8947	$10.89	$10.90	$10.90
Purchase #5	$96.55	7.861%	$104.1398	$104.14	$104.15	$104.10
Purchase #6	$158.66	9.297%	$173.4106	$173.41	$173.40	$173.40
Purchase #7	$25.57	5.441%	$26.9613	$26.96	$26.95	$27.00
7 purchase totals =	$577.72		$627.4714	$627.46	$627.50	$627.40